The Linden Looper in Western Colorado
The linden looper, Erannis tiliaria, defoliated several stands of broadleaf trees and shrubs in Garfield and Delta Counties during 2006. Several other areas were defoliated in Garfield, Routt and Mesa Counties during 2007. There is little information on this insect in the Rocky Mountain region. The insect is well known in the eastern US, where it defoliates scattered woodlots and forest stands each year.
Linden loopers are native to the eastern USA. The scientific literature describes their range west to the Rocky Mountains and north to Canada, so they can probably be considered native to Colorado.
A single year of defoliation will not seriously harm trees and shrubs, but repeated years of defoliation, or defoliation coupled with other stresses such as drought can impact tree health. The aesthetic impact of defoliation can be quite high. This picture shows defoliation near Vega Reservoir (Mesa County) during the summer of 2007.
The decision to control linden loopers must take into account the amount of defoliation, the growth stage of the larvae, stand health, cost and aesthetic considerations. Individual trees in a landscape setting can be protected from egg laying by applying a sticky band of tanglefoot around the trunk of the tree in the fall before females emerge. This approach is not feasible in a forest setting. Several insecticides - biological, growth regulators and broad spectrum are labeled for use in forest settings. Contact your local Extension or State Forest Service agent to discuss options for your particular situation.
The larvae of linden loopers feed on many species of broadleaf trees and shrubs. They seem to prefer oak, serviceberry, and chokecherry in western Colorado. They reportedly fed on aspen in the 2007 Routt County outbreak near Hayden. They are reported from narrow leaf cottonwood at the 2007 Collbran site. This picture was taken on a north facing stand of several species of shrubs and small trees near Rulison in 2006.
Linden looper larvae eat the blade of the leaf, leaving the midrib. Defoliation can be complete when the insect is in an outbreak situation. Healthy trees will flush new leaves. There is one generation per year, with the peak of defoliation appearing in early June at most sites. This picture shows damage on Gambel oak at Rulison in 2006.
Newly hatched linden looper larvae are tiny, as this picture shows. If control efforts are taken, this is the best stage to apply a residual insecticide. Dennis Jones took this picture near Vega Reservoir on May 21.
Newly hatched larvae move on silken strings. The presence of these strings makes an infestation visible well before damage is apparent. Dennis Jones took this picture on his property near Collbran on May 21, 2008.
Webbing created by early instar linden loopers in serviceberry. Dennis Jones took this picture near Collbran on May 21, 2008.
Linden looper larvae are inchworms, with only two prolegs. They move in a looping fashion. Mature larvae are about 1 1/2 inches long. The bottom side of the abdomen is yellow, the topside streaked with black, blue and yellow linear lines. The head capsule is brown. Young larvae drop on strings when disturbed.
Larvae drop to the ground when mature and pupate in the soil. The naked pupae are 7/16 inch in length. The larvae remain in the pupal stage through the summer. They emerge as moths in late September and early October. The pictured pupa was reared from a larva in 2006.
Adult linden loopers emerged in late September and early October in the Collbran area in 2007. Egg laying occurred throughout the month of October.
Males (top picture) are brown moths with a wing span of a little more than 1/2 inch. They fly at night. Females (bottom) are wingless and at first glance do not look like moths. They can be found on the trunks of trees during the daytime during the fall activity period.
Moths emerge from the pupal cells in the soil and mate. The females must crawl up the trunk of nearby trees to lay eggs. Eggs are laid in cracks in the bark and other protected areas on the trunk of the tree.
This page was updated on April 26, 2014